1. Field of the Invention
The present invention relates to a turn signal switch device attached to a steering column or the like of an automobile and serving as a direction indicator and, more specifically, it relates to a mechanism for releasing an excess load when, in a cancel operation for automatically restoring an operating lever provided in the turn signal switch device from an operating position to a neutral position, an external force preventing the automatic restoring is applied to the operating lever.
2. Description of Related Art
In the turn signal switch device of an automobile, the base end of an operating lever is rotatably supported by a housing integrally formed with the steering column or the like, and the forward end of this operating lever is rotated from a neutral position to a right or left direction indicating position, whereby a right-turn or left-turn lamp is caused to blink. In such a turn signal switch device, to retain the operating lever at three positions of the right and left direction indicating positions and the neutral position, the inner surface of the housing is provided with a cam surface, and the operating lever is provided, through the intermediation of a spring, with a pressurizing member to be engaged with the cam surface. Further, there is provided a cancel mechanism for automatically restoring the operating lever to the neutral position when the steering wheel is turned in a returning direction which is a direction opposite to the indicated direction, with the operating lever rotated to the right or left direction indicating position.
The description will be made of drawings showing such a cancel mechanism according to the prior art. FIG. 6 is a cross sectional view schematically showing the construction of the turn signal switch device; FIG. 7 is a front view of a movable member provided in the turn signal switch device; and FIGS. 8A and 8B are schematic diagrams illustrating the operation of a cancel mechanism provided in the turn signal switch device.
With reference to FIGS. 6 to 8, the description will be made of the turn signal switch device according to the prior art. A housing 100 is substantially box-shaped, made of insulating resin, and is secured to a column (not shown), which is a stator member of a steering device, and the like. On the bottom surface of the housing 100, a guide shaft 101 and a support shaft 102 are formed to protrude at a predetermined interval, and at the end of the bottom surface, a cylindrical protrusion 106 is provided. Also, inside the housing 100, there is formed a V-shaped cam surface 109 having a pair of lock portions 109a on the right and left sides.
A second lever member 104 is made of insulating resin; has an outside shape being substantially rectangular; has a first opening 104b and a second opening 104c; between these two openings, there is provided a shaft hole 104d; and at the outer end of the first opening 104b, a connection pin 104a is formed. A shaft hole 104d of the second lever member is rotatably fitted in a support shaft 102 provided in the bottom surface of the housing 100.
The first lever member 103 is made of insulating resin, is square bar-shaped, and has a first elongated hole 103a and a second elongated hole 103b which are arranged in a line in the longitudinal direction. Further, at the front and rear ends of the first lever member 103 in the longitudinal direction, there are provided an abutting portion 103c and a cam 103d respectively, the cross sectional configuration of the cam 103d being semi-circular. The first elongated hole 103a of the first lever member 103 is slidably fitted in the guide shaft 101 formed on the bottom surface of the housing 100, and the second elongated hole 103b is slidably fitted in a connection pin 104a provided in the second lever member 104 to connect the first lever member 103 with the second lever member 104.
In a torsion coil spring 105, wire formed of elastic material is wound several turns, both ends are left in a straight line state, the wound portion is fitted in and fixed to a protrusion 106 of the housing 100, one of the straight line-shaped portions at both ends is fixed to the end of the bottom surface of the housing 100, and the other is engaged with the first lever member, whereby the first lever member 103 is adapted to be elastically biased in the direction that goes away from the second lever member 104 in the longitudinal direction of the first lever member 103.
A holder 110 is a structure made of insulating resin, is mounted within the housing 100, has support shafts 108 at both ends, and is provided with a cylinder 110a protruding,on the front side. Inside the cylinder 110a, a driving member 111 is slidably held, and the forward end of this driving member 111 is constantly held in press contact with the cam surface 109 of the housing 100 by a spring (not shown).
An operating lever 107 is made of insulating resin, is substantially cylindrical, the base end is fitted in support shafts 108 at both ends of the holder 110, and is supported by the housing 100 so as to be rotatable together with the holder 110 in the direction indicated by the arrow a or b.
A movable member 115 is constructed such that, at the center of a rectangular plate member made of insulating resin, there is integrally provided a cylinder portion 115a vertically to the plate member; at the top end, there are provided a pair of engagement claws 115b; the wound portion of a return spring 116 wound is wound around the cylinder portion 115a; and both arms of the return spring 116 are restrained by a pair of engagement claws 115b and 115b. Inside the cylinder portion 115a, a cylinder 110a of the holder 110 is rotatably housed. The both arms of the return spring 116 are restrained by a pair of engagement claws 115b and 115b and engaged with the holder 110, whereby the movable member 115 is constantly biased toward a predetermined stable position with respect to the holder 110. Therefore, normally the rotation of the operating lever 107 rotates integrally the movable member 115 together with the holder 110. Further, the movable member 115 is provided with a cam 112 having a semi-circular cross sectional configuration and a receiving portion 113, and the cam 112 is opposed to the cam 103d of the first lever member 103, the receiving portion 113 protruding in the second opening 104c of the second lever member 104.
Next, the description will be made of an operation of the turn signal switch device, constructed as described above. When the operating lever 107 is at the neutral position, the forward end of the driving member 111 abuts the central valley of the cam surface 109, and is stably held at the position by the elasticity of a spring (not shown). At this time, as shown in FIG. 8A, the cam 112 of the movable member 115 on the operating lever 107 side and the cam 103d of the first lever member 103 are in contact with each other at their apexes, and the first lever member 103 retracts against the biasing force of the torsion coil spring 105. Thus, the abutting portion 103c of the first lever member 103 is positioned outside the rotation path of a cancel protrusion 114 rotating with the steering wheel; even if the steering wheel is turned in this state, the cancel protrusion 114 does not abut the abutting portion 103c of the first lever member 103, and the operating lever 107 is maintained at the neutral position.
When the operating lever 107 is rotated from this neutral position in the direction of the arrow a or the arrow b in FIG. 6, the forward end of the driving member 111 moves over the slope of the cam surface 109 and is engaged with the lock portion 109a, and stably held at the position by the lock portion 109a. For example, when the operating lever 107 is rotated in the direction of the arrow b in FIG. 6, the movable member 115 integrally rotates in interlock with that, and the cam 112 and the receiving portion 113 of the movable member 115 are displaced from the position shown in FIG. 8A to that shown in FIG. 8B. As a result, the cam 112 is detached from the apex of the cam 103d of the first lever member 103, and the first lever member 103 receives the elastic force of the torsion coil spring 105 to advance along the longitudinal direction of the both elongated holes 103a and 103b, the abutting portion 103c advancing into the rotation path of the cancel protrusion 114. Further, with the rotation of the operating lever 107 in the direction of the arrow b, switching operation is effected on a contact (not shown), and the right-hand turn lamp blinks.
When the steering wheel is turned in the opposite direction (the direction of the arrow in the drawing) in the right-hand turn state shown in FIG. 8B, the cancel protrusion 114 abuts the abutting portion 103c of the first lever member 103 during the return operation. As a result, the first lever member 103 rotates clockwise as seen in the drawing around the guide shaft 101, and the torque is transmitted from the second elongated hole 103b to a second lever member 104 through a connection pin 104a, and the second lever member 104 rotates clockwise around the support shaft 102, so that the second opening 104c of the second lever member 104 is rotated and displaced upward as seen in the drawing. As a result, the periphery of the second opening 104c upwardly pressurizes the receiving portion 113 of the movable member 115, so that the driving member 111 is detached from the lock portion 109a of the cam surface 109 and moves toward the central valley, and the operating lever 107 and the first and second lever members 103 and 104 are automatically restored to the neutral position shown in FIG. 8A.
At this time, when some force preventing the automatic restoration is applied to the operating lever 107 in the right-hand turn state shown in FIG. 8B, for example, when the steering wheel is turned in the opposite direction with the operating lever 107 being pressed by the driver, the periphery of the second opening 104c upwardly pressurizes the receiving portion 113 of the movable member 115 as described above. However, the operating lever 107, which is being pressed, is not automatically restored. In this case, the movable member 115 rotates the peripheral surface of the cylinder 110a of the holder 110 from the stable position to the retracted position against the biasing force of the return spring 116. And, when the cancel protrusion 114 passes the abutting portion 103c of the first lever member 103, the movable member 115 is automatically restored from the retracted position to the stable position by the biasing force of the return spring 116, so that it is maintained in the right-hand turn state shown in FIG. 8B again.
In the above-described conventional turn signal switch device, when some force preventing automatic restoration is applied to the operating lever 107 when automatically restoring the operating lever 107 from the operating position to the neutral position, an excess load generated between the second opening 104c of the second lever member 104 and the receiving portion 113 of the movable member 115 is released (absorbed) by the rotation of the movable member 115, so that it is possible to prevent breakage of the power transmission system including the first and second lever members 103 and 104 and the receiving portion 113. However, to install such a mechanism, it is necessary to provide the rotatable movable member 115 and the return spring 116 which elastically biases the movable member 115 toward the stable position, and the number of parts increases due to the movable member 115 and the return spring 116. Further, due to the mounting space for the movable member 115 and the return spring 116, the size of the turn signal switch device is enlarged.
Therefore, it is an object of the present invention to provide a small-sized turn signal switch device easy to assemble by reducing the number of parts.
In accordance with the present invention, there is provided a turn signal switch device comprising: a housing equipped with a cancel protrusion outward which rotates in accordance with a steering wheel operation; a cam surface formed within the housing; first biasing means for applying a biasing force toward the cam surface; a holder rotatably mounted to the housing; an operating lever integrally provided in the holder and provided extending outwardly of the housing; a first cam integrally provided in the holder; a second cam which abuts the first cam in a direction toward a rotation path of the cancel protrusion; a first cancel lever integrally formed in the second cam, which is engaged with and mounted to the housing so as to be displaceable and rotatable until the rotation path of the cancel protrusion is reached; second biasing means which applies a biasing force so as to displace the first cancel lever in accordance with a displacement in an abutted position between the first cam and the second cam toward the rotation path of the cancel protrusion; and a second cancel lever which is rotatably engaged with each of the first cancel lever and the housing so as to rotate in the same direction as the direction of rotation of the first cancel lever in interlock with the rotation of the first cancel lever, wherein the second cancel lever is engaged with and mounted to the holder in such a manner that a direction of rotation of the second cancel lever is opposite to that of the holder, and wherein a center of rotation of the second cancel lever with respect to the housing is made displaceable within a predetermined range from a neutral position and the center of rotation displaced is made automatically restorable to the neutral position.
According to this structure, it is possible to provide a small-sized turn signal switch device which is capable of reducing the number of parts and easy to assemble.
Also, the structure is arranged such that the center of rotation of the second cancel lever is a protrusion shaft or an elongated hole, the protrusion shaft or the elongated hole is inserted into an elongated hole or a protrusion shaft provided in a bottom plate of the housing, and is caught between both ends of a spring mounted to the bottom plate or the second cancel lever in order that the both ends may be exposed in the elongated hole to hold the protrusion shaft at a central position of the elongated hole; the operating lever is caused to be automatically restored from an operating position to the neutral position in interlock with the rotating operation of the first and second cancel levers in such a state; and when an excess load for preventing automatic restoration from the operating position to the neutral position is applied to the operating lever, the protrusion shaft is moved from the central position of the elongated hole to the end position against a resilient force of the spring, whereby the first and second cancel levers are allowed to rotate.
According to this structure, it is possible to reduce the number of parts and to provide a small-sized turn signal switch device easy to assemble.
Also, the structure is arranged such that the center of rotation of the second cancel lever is a rotating shaft, which is a protrusion shaft; the rotating shaft is inserted into an elongated hole provided in the bottom plate of the housing and is caught between both ends of a spring mounted to the bottom plate in order that the both ends are exposed in the elongated hole to hold the rotating shaft at a central position of the elongated hole; the operating lever is caused to be automatically restored from the operating position to the neutral position in interlock with rotating operation of the first and second cancel levers in such a state; and when an excess load for preventing automatic restoration from the operating position to the neutral position is applied to the operating lever, the rotating shaft is moved from the central position of the elongated hole to an end position against the resilient force of the spring, whereby the cancel levers are allowed to rotate.
According to this structure, it is possible to reduce the number of parts, and to provide a small-sized turn signal switch device easy to assemble.
Also, the spring is provided on a protruded portion on a back surface side of the bottom plate, and between both ends of the spring, a stopper member having the substantially same width as a diameter of the rotating shaft which is provided on the back surface side of the bottom plate and the rotating shaft are caught.
According to this structure, since the back surface side of the bottom plate is used, it is easy to secure space for forming the protruded portion and the stopper member.
Also, the spring is a coil spring having straight lines at the both ends respectively, and between the both ends, the rotating shaft and a stopper member having the substantially same width as the diameter of the rotating shaft are caught.
According to this structure, since a general coil spring is used, it is easy to handle.
Also, the stopper member is a wall, and this wall is provided between the elongated hole and the protruded portion integrally with the bottom plate.
According to this structure, since the wall, which is a stopper member, is between the elongated hole and protruded portion, it is easy to mount by engaging the spring with the stopper member.
Also, the first biasing means is a coil spring.
According to this structure, since a general coil spring is used, it is easy to handle.
Also, the cam surface is shaped like a letter V.
According to this structure, the member pressurized easily takes a neutral position because of the shape of the letter V.